Ubuntu auto detect proxy pac config file

proxy.pac

function FindProxyForURL(url, host)
{
  if (isInNet(myIpAddress(), "1.2.3.0", "255.255.255.0")) {
    if (isInNet(host, "192.168.0.0", "255.255.0.0"))
      return "DIRECT";
    if (shExpMatch(url, "http:*"))
      return "PROXY my.proxy.com:8000" ;
    if (shExpMatch(url, "https:*"))
      return "PROXY my.proxy.com:8000" ;
    if (shExpMatch(url, "ftp:*"))
      return "PROXY my.proxy.com:8000" ;
    return "DIRECT";
  } else {
    return "DIRECT";
  }
}